The present invention relates to an actuating device, more precisely relates to an actuating device having a moving body, which is moved and guided by a rail or a guide section.
In conventional actuating devices having moving bodies guided by rails, the moving bodies are pressed onto the rails so as to smoothly move the moving bodies without plays.
One of the conventional actuating devices is disclosed in Japanese Patent Gazette No. 2002-122136. Balls are provided between a rail and a moving body. The moving body is moved along the rail by rolling the balls (see paragraphs 0002 and 0019 and FIGS. 1 and 2). The balls, whose sizes are slightly larger than a clearance between the moving body and the rail, are fitted in the clearance so as to apply a pressing force to the moving body and the rail (see the paragraph 0002).
By the method of applying the pressing force disclosed in the Japanese gazette, the clearance between the rail and the moving body is filled with the balls, so that plays can be removed. Therefore, even heavy goods, whose weight are several hundred Kg or more, can be smoothly conveyed by the actuating device.
However, in the actuating device disclosed in the Japanese gazette, the balls, whose sizes are larger than the clearance between the metallic rail and the moving body, are fitted in the clearance, so that the balls are deformed. Thus, rolling resistances of the balls or a dynamic resistance of the moving body must be increased, and energy consumption for moving the moving body must be large. The rail, the moving body and the balls must have high durability, and they must be case-hardened so that a manufacturing cost of the device must be increased. To generate a great driving force, the device must be large and heavy. Further, a large amount of lubricant must be frequently applied so as to reduce the rolling resistances and prevent damage of the rail, the moving body and the balls, so that a running cost and a maintenance cost of the device must be increased.
In case of conveying light goods, the large and high cost device disclosed in Japanese Patent Gazette No. 2002-122136 is not required. For example, an actuating device for conveying light goods is disclosed in Japanese Patent Gazette No. 7-54843. The actuating device comprises: a moving body; a rail for guiding the moving body; contact bodies, which are provided to the moving body and contact the rail; and biasing members for pressing the contact bodies onto the rail (see a paragraph 0078 and FIGS. 1 and 2).
By the method of pressing the contact bodies onto the rail, a dynamic resistance of the moving body can be smaller than that of the device disclosed in Japanese Patent Gazette No. 2002-122136. Further, the device can be made of light materials, and a manufacturing cost, a running cost and a maintenance cost of the device can be reduced.
However, when an external force, which is greater than elasticity of the biasing members, is applied to the contact bodies, the biasing members are deformed so that the moving body cannot be moved smoothly.
To solve this problem, the biasing members having great elasticity may be employed so as to increase the force for pressing the contact bodies onto the rail. However, frictional resistances between the contact bodies and the rail must be increased, so that the biasing members must be large, the device must be large and heavy, the manufacturing cost and energy consumption of the device must be increased.